A test for comparing the means of two samples; also known as the "Student t-test" after the pseudonym of its inventor.
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2answers
50 views
Estimating the covariance of the means from two samples?
Let there be two samples of size $n$, $x_i$ and $y_i$ from two different normal distributions.
What is $\operatorname{cov}(\bar X_n, \bar Y_n)$? And how can it be estimated?
The motivation for my ...
2
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1answer
31 views
Comparing results for computer and pen and paper writing
I am conducting a study to examine the differences between writing paragraphs in English among junior high school students in Japan.
We collected writing samples from four classes, approximately 38 ...
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0answers
35 views
Reconstructing time series data with missing values from external data source
I have a 100 year time series. But the first 30 years are missing. So I correlated the 70 years that I have with another (100 year) time series to predict back / reconstruct the missing values. For ...
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0answers
18 views
Measuring spatial overlap in 2 different ways - paired t-test?
I have collected spatial data (GPS points and foraging heights) for a bunch of territorial animals. Until recently, these types of data were only analyzed in two dimensions (2D). However, 3D analysis ...
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0answers
20 views
Is the t-test really robust to shape of distribution? [duplicate]
Can I use the t-test to compare means between groups (N=300) if data is not normally distributed?
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2answers
351 views
How are regression, the t-test, and the ANOVA all versions of the general linear model?
How are they all versions of the same basic statistical method?
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4answers
322 views
Standard deviation larger than mean
I am trying to test if there has been a significant change in the weight of two groups, one without exercise and one with exercise.
The two samples have large spread, which creates a standard ...
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3answers
48 views
Testing whether two groups formed from a continuous variable differ on a binary outcome
18 people, who have been divided into 2 groups based on the semiquantitative expression of a protein (low vs high).
Group 1 (low protein levels) has 6 people, Group 2 (high protein levels) has 12 ...
2
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0answers
16 views
How to test significance of pre-post difference scores on 8 measures (1 group)
I have a set of pre and post treatment scores on 8 measures. I'd like to test which of these show significant improvement after treatment. If I use within-subjects t tests it will mean carrying out 8 ...
2
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1answer
42 views
Should I use a paired or unpaired t-test for this problem?
I tested 5 objects with two different devices each, but on the last test for the second device, there was an error so the value was unusable (ie on objects 1-5, first device series was 1,1,2,2,3 and ...
4
votes
1answer
58 views
Replace t-test with modified z-test - anyone ever seen this?
I just read about a procedure I'd never heard of, and was wondering if anyone has had any experience with it. In Donald Berry's "Statistics" book, he presents an alternative to doing a t-test by ...
2
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1answer
64 views
Advice on the statistical analysis of clinical data using summary statistics, t-tests, ANOVA, and linear regression
I need some help with the statistical analysis of a study of a particular surgery to remove a particular cancer. I am using the statistical program R to conduct my analysis. My data are saved in the ...
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1answer
73 views
Can I use t-test for interaction in a two-way factorial ANOVA?
I have a two-way factorial design, with factors treatment (A vs. B) and time (T1 vs. T2). The same subject was measured twice, at T1 and T2, so I have repeated measurements. I am interested to see ...
0
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1answer
29 views
How can I find tendencies in specific cases between two groups?
So, I'm doing this project where we are investigating whether social networks can influence peoples distinctiveness. Briefly summarized, we have primed a group with a social media and another is the ...
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4answers
67 views
T-test and the number of observations
I have a sample of the number of bank loans issued each year from the period 2004-2012. I have split the sample in two (2004-2008 and 2009-2012) and want to test if the number of bank loans issued in ...
1
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1answer
39 views
What is the distinction between “relationships” and “differences” (particularly in the context of group differences on a numeric attribute)?
What is the distinction between a relationship and a difference in the context of statistics - if you have a nominal variable and an interval variable, when should you use a correlation to measure the ...
2
votes
1answer
46 views
Comparison of two Simpson indices using t-test
I would like to compare two Simpson Indices from two different populations. I have calculated their variance, as it is done in the original paper by Simpson regarding measures of diversity and I have ...
0
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0answers
32 views
Repeated 100x 10-fold cross validation, what is the sample size when doing an significance test?
I iterated my 10-fold cross validation 100 times for several methods. Now I want to use a t-test to test if the results are significant. However, I'm not sure what the sample size is.
Is the sample ...
1
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1answer
45 views
Correcting for Type 1 error in multiple paired t-tests?
I'm wondering whether or not I should adjust the significance level of paired t-tests due to multiple tests (to avoid the possibility of Type 1 error), although the tests are independent. Here's what ...
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0answers
38 views
How to test for differences in 3 related measures assessed pre- & post- treatment on the same sample?
I am designing a study to compare whether one specific treatment improves Quality of life. I am using a convenience sample ($N=20$). I hope to administer three ...
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0answers
96 views
Which statistical test should i use? pre-post intervention comparisions and post-post comparisons
In my experiment I compare the jump height of participants pre and post 2 separate interventions.
All participants completed baseline measures of jump height. Participants then underwent a training ...
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0answers
17 views
Testing the effect of spatial differences
I have a closed room. I release some bacteria in the middle of it and let it settle onto previously located plates on the floor. Once the bacteria settles I collect the plates and count up how many ...
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0answers
38 views
Evaluate Quantile Regression results and t-stats at different levels.
I have a few questions regarding quantile regression and how to interpret the results. I have several independent variables and I want to figure out which combination of variables have the highest ...
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1answer
82 views
Confidence interval in two tailed t test
If I am doing a two tailed $t$ test, i.e my null and alternate hypothesis are
$$H_0: \mu = 0$$
$$H_1: \mu \neq 0,$$
then would I choose and $\alpha$ value of $0.05$ for a $95$% confidence interval ...
1
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1answer
94 views
ANOVA or multiple t-tests when comparing pre-existing group means?
I understand that Anova is preferred over multiple t-tests, but what exact is multiple t-tests?
Examples involving taking groups from the population (with the same population mean):
We have groups ...
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2answers
73 views
Is it possible to use a two sample $t$ test here?
I want to do statistical analysis to compare the results of the different specimen sizes (which I am comparing) with each other. Seeing as I have at least 12 specimens for each specimen size, I ...
3
votes
1answer
61 views
How to back-calculate change from baseline from a p-value for a paired t test
I have a result from a study in a research paper which gives a mean/SD for 2 time points (pre & post treatment), and a p-value based on a paired-samples t-test. What I want to calculate is the SD ...
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1answer
121 views
Independent paired t-test -> Mann Whitney U
Just a quick introduction, I'm rubbish at stats.
I asked a question before which was very well answered but I have since modified the experiment in a way that confuses me as to which test I should ...
5
votes
2answers
185 views
Can a sample be too large for ANOVA or a t-test?
I have close to a million data sets and whenever I run mean comparison test, either ANOVA or a t-test, I get a significance level of less than .0001 on SPSS. I'm concerned that my sample is so large ...
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1answer
94 views
What statistical test to use for my questionnaire
I have to do some statistical tests on a questionnaire and don't know which tests i need to do. The questionnaire have been marked as right or wrong and I have about 60 peoples results. The tests i ...
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2answers
31 views
Percent reduction between two groups
We'd like to express how much better A performs when combined with B. Is it as simple as comparing the averages of the two groups?
When tested, widget A has a range of results from 36 to 43 with an ...
0
votes
1answer
443 views
How do I interpret the results from the F-test in excel
I have a fairly simple question regarding the interpretation of the F-test in Microsoft Excel.
Let't say these are the results of my F-test:
http://i.imgur.com/ZLzEQih.jpg
I am now wondering how to ...
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1answer
75 views
How to calculate the percentage of a sample that is delayed
I'm working on a thesis and I'm using a bit statistics to process the data. I have a certain population and in one sample (N=250) I measure the time it takes to reach a goal. Then I change something ...
2
votes
1answer
55 views
T-test on ranks vs Mann WHitney U-test equivalence
What does it mean when people say that a T-test performed on ranked data is equivalent to a Mann WHitney U -test? Does that mean they just test the same hypothesis/are useful in the same situations or ...
2
votes
2answers
148 views
Prove F test is equal to T test squared
I need to show that F test is equal to T test squared, when the T test is for 2 independent groups and assuming variances are equal.
I know that $F=\frac{MSB}{MSW}=\frac{SSB/k-1}{SSW/N-K}$
and I know ...
0
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0answers
29 views
method and needed tests for assumption in analyzing a paired sample Likert measure?
I am writing an exploratory paper considering an argument that a certain reaction that can arise in the viewing of art can serve as an empirical indicator that another particular cognitive process has ...
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0answers
75 views
Comparing max/min over several time points against baseline
I have a time-series dataset with repeated measurements (multiple subjects). I have around 100 variables to test. The question is - Is something happen in a time range independently on exact time? For ...
0
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1answer
76 views
Can I use paired sample t-test for the following problem?
Suppose there is an experiment that in each trial returns a two vector of probabilities of size $n$. In each trial I select uniformly a number from ${1,\cdots, n}$ and compare that element in this two ...
2
votes
1answer
118 views
Using z scores in paired t-tests and regression analysis
I have one group of participants measured on a health outcome scale at two different time points. I first want to see whether there is a significant difference between time 1 and time 2 on this ...
1
vote
1answer
94 views
Why is my t-test intuition so far from reality?
Interpretation of t-test value (2 tailed): ~20% chance that these results could have been obtained randomly.
My intuition: MEAN_2 - MEAN_1 = ~3% of MIN(STD_1, STD2). Calculate area under normal ...
0
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2answers
53 views
Paired Differences T-tests for Odd number of Observations
Suppose we have $m$ baseline data points and $n$ post-baseline data points where $m < n$. This is for one subject. Is it possible to perform a paired t-test on this data even though $m+n$ is odd? ...
2
votes
2answers
98 views
How do I analyze a z-score to determine a difference?
My data are in SPSS. I teach in a nursing program.
During their junior year, 68 students participated in a simulation scenario for heart failure. They were by rated by observers (0/1, did not do/did ...
1
vote
1answer
34 views
Why a different F-value for the same factor in a one-way vs. two-way ANOVA?
From what I understand, the null hypothesis for One-way ANOVA is:
There is no difference in the means of factor A
The null hypothesis for Two-way ANOVA is:
There is no difference in the means ...
1
vote
1answer
30 views
Two (or multiple) t-test replaced with a single pairwise.t.test()?
This is an artificial example. I want to compare the Income of the same group of people (i.e. "pairing") while they were working in US, Spain, and Nigeria. In other words, I use the "US" income as a ...
1
vote
1answer
87 views
All my observations are identical. Use a non-parametric test?
I was doing test for normality on variables and came across one that had identical values for each observation. I can't do a normality test. I plotted the kernel density and it looks normal, however ...
0
votes
1answer
86 views
What type of statistic should I use to compare ratios in my experiment?
I have performed an experiment to analyse the ratio of intronic versus exonic levels for 1000 transcripts after treated the cells with a drug and compare my results with untreated cells . Each ...
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0answers
40 views
t-test for paired and randomised distributions
So I have two sets of profiles scores which are as below
...
2
votes
1answer
240 views
Mann Whitney or two tailed t-test
I am new to statistics and am in need of some help. I am running a study where I am providing two groups with surveys to test for their perceptions using a Likert Scale. One group I'm testing prior to ...
0
votes
1answer
52 views
Testing if males and females pronounce particular sound the same way
I have a sample size of 360 respondents, divided to 180 males and 180 females. I want to find out whether there is a significant difference between their pronunciation of a particular sound. Being a ...
0
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1answer
103 views
How are the p-values of the GLM in R calculated?
I have been running some binomial logistic regressions in R on a data set and I realised that the p-values of the estimated coefficients are not computed based upon a Normal distribution. For e.g. I ...
